Global energy demand is increasing, which is putting pressure on the oil and gas industry to improve the effectiveness of extraction from mature fields and to explore fields that are smaller and located in more challenging environments, including ultra-deepwater environments. The development of subsea oil and gas fields requires specialised equipment that must be robust and reliable to safeguard both the equipment itself and the environment and to make the exploitation of the subsea hydrocarbons economically feasible. The deployment and repair of subsea equipment requires specialised vessels equipped with diving and robotic equipment and so interventions to replace or repair such equipment is generally very expensive.
To monitor the extraction of product from subsea wells, the environmental conditions therein are monitored by pressure and/or temperature sensors located downhole at the base of the wellbore. In addition, wellhead and wellbore equipment to control the flow of product is electronically controlled by command signals from the wellhead.
The data transfer requirements between the top side and subsea equipment in order to control the subsea equipment and retrieve data collected by the subsea equipment can be very high. For example, in order to control the subsea well equipment, currently, data retrieved from the subsea equipment is sent top side were the control systems and logic solving systems are based. Once this data has been processed by the control and logic solving systems, control signals are then sent back subsea to control the equipment at a wellhead.
A single umbilical is usually required to carry data and control signals from subsea to topside and vice versa for a number of well assemblies. Usually, the subsea network connecting the umbilical to the equipment at various locations subsea comprises a number of point-to-point data connection cables such that a subsea network having a star-like topology is used to route the control signals received on the umbilical to the subsea locations.
As a result, the data transfer requirements for umbilical can become very high. Even though new umbilical deployments often include the installation of fibre-optic links between the subsea and topside level, giving more bandwidth, this is still the most costly place to transfer data as the operational bandwidth required to monitor and control the well assemblies can consume a significant proportion of the channel capacity of the umbilical. The channel capacity of the umbilical is often constrained due to the long distances over which data can be transferred, the level of redundancy and high requirement for error correction. With an increasing volume of data being generated both topside and subsea, the operational demands on umbilicals are increasing such that there is little spare capacity in the umbilical to handle non-operation critical, lower priority data transfers.
For example, it is often required to transfer data from a surface facility (“top side”) to subsea to update well equipment, either downhole or at the wellhead, with often large files of new software, configurations datasets, etc. Currently, in order to update equipment, this data is routed from topside to subsea in a point-to-point data transfer using whatever low priority bandwidth is free on the umbilical. File transfer support from topside to the wellhead and well assembly equipment is often not robust and so these transfers can be problematic. In addition, as each equipment requires updating individually, the time required to transfer software updates for larger numbers of identical equipment can often be a number of days. Alternatively, the operations-critical data may be interrupted to allow software data transfers to take priority. However, this is undesirable and disruptive.
As a result, transferring large amounts of non-time critical and non-operation critical data subsea using an umbilical can be a very long, problematic and difficult process such that it is impractical and costly to transmit a large volume of software updates and configuration dataset updates subsea by the umbilical.
Similarly, the volume of data collected by well sensors and instruments subsea is ever increasing. This logging and monitoring data, while potentially very useful for well analysis and control, is often not capable of being transmitted topside due to the bandwidth limitations on the umbilical and so a large amount is typically discarded.
The electronics for interfacing with the subsea equipment to process the received sensor signals and to provide the control signals to the well equipment are generally provided within a subsea electronic module (SEM) that is disposed within a subsea control module (SCM) provided at the wellhead. These SEMs form nodes in the subsea network for routing data to and from topside via the umbilical.
The SEM generally provides a plurality of physical cards that support electronic assemblies (such as printed circuit boards, PCBs) arranged in slots connected by a backplane all contained within a robust housing that can withstand the extreme high pressure environment at the subsea wellhead. The electronic assemblies of the cards each perform different electronic functions for interfacing with different well equipment from different manufacturers. In the new generation of SEMs, there is now a quite tight coupling between the various cards in a SEM mode, sharing common parts of their software images, having a single configuration database (CDB) for the node and so forth. However, the SEM nodes currently are quite separate from each other in their functionality in the network other than to route data in the network to and from the umbilical.
European patent application publication number EP2458140 discloses providing a data store at an SCM for data monitoring the condition of the subsea equipment. The data store allows for storage and sending of the condition monitoring data up the umbilical separate from client-sensitive data.
It is in this context that the present invention is devised.